This invention relates to motor control systems, and in particular, to a command module for allowing a user to remotely transmit commands to and receive commands from a motor control which, in turn, controls the starting, stopping and speed of an AC induction motor.
There are two basic approaches for controlling the starting, stopping and speed of an AC induction motor. In a first approach, an adjustable frequency controller is interconnected to the AC induction motor. The adjustable frequency controller is comprised of an inverter which uses solid state switches to convert DC power to stepped waveform AC power. A waveform generator produces switching signals for the inverter under control of a microprocessor. While adjustable frequency controllers efficiently control the motor speed and the energy used by an AC induction motor, use of such types of controllers may be cost prohibitive. Further, since many applications of AC induction motors do not require sophisticated frequency and voltage control, an alternative to adjustable frequency controllers has been developed.
An alternate approach to the adjustable frequency controller is the soft starter. Soft starters operate using the principal of phase control whereby the three phase main supply to the AC induction motor is controlled by means of anti-parallel thyristor switches in each supply line. In phase control, the thyristor switches in each supply line are fired to control the fraction of the half cycle over which current is conducted to the motor, known as the conduction period. The non-conducting period of each half cycle (known as the hold-off angle or the notch width) is visible as a notch in the voltage waveform at each motor terminal. During this period, no current flows to the motor terminals. To end the non-conducting period, the thyristor switches in the supply line to the motor terminals are fired to restart their conduction. The conduction through the thyristor switches continues until the current, once again, becomes zero at some point in the next half cycle and the thyristor switches reopen. According to the principles of phase control, by varying the duration of the non-conducting period, the voltage and current supplied to the AC induction motor may be controlled. As is known, a single microprocessor has been used to fire the thyristor switches in order to control the voltage and current supplied to the AC induction motor.
In addition to controlling the starting, stopping and speed of the AC induction motor, the microprocessors in the adjustable frequency controller and the soft starter microprocessors execute intensive control algorithms to effectuate proper motor control. In order to effectuate the numerous calculations required at an acceptable computational speed, high performance microprocessors are required. The types of high performance microprocessors are expensive and increase the overall cost of the motor control. Therefore, it is highly desirable to provide a motor control system which provides the desired control efficiency of electric motors at a lower cost.
In addition, use of a single microprocessor in motor control applications limits the flexibility of such motor control. Heretofore, motor controls have been built as single, integral units. Such units provide for limited input and output options for the user. As a result, prior art motor controls limit the user""s ability to monitor certain operation parameters or require special hardware to display or control certain operating parameters. As a result, it is highly desirable to provide a motor control which allows greater flexibility for a user.
Therefore, it is a primary object and feature of the present invention to provide a motor control system which incorporates distributed processing to reduce the cost and improved performance of the motor control system.
It is a still further object and feature of the present invention to provide a motor control system which increases the flexibility to the users thereof.
It is a still further object and feature of the present invention to provide an input/output device for a motor control system which is simple to use and inexpensive to manufacture.
In accordance with the present invention, a command module is provided for allowing the user to sends commands to one or more motor controls wherein each motor control is operatively connected to a communications network. The command module includes a micro-controller and a plurality of selection devices operatively connected to the micro-controller. Each selection device is moved between a first non-actuated and a second actuated position wherein the selection device provides an activation signal to the micro-controller which, in turn, generates a command signal in response thereto. A configuration device is interconnected to the micro-controller. The configuration device has a plurality of discreet settings such that the command signal generated by the micro-controller in response to the receipt of the activation signal is predetermined by the setting of the configuration device. A communications link interconnects the micro-controller to the communications network.
It is contemplated that the configuration device includes a dip switch movable between first and second settings. The micro-controller may also include a universal asynchronous receiver/transmitter. The communications link may include a transceiver operatively connected to the universal asynchronous receiver/transmitter in order to connect the micro-controller to the communications network. The communications link receives packets of data from the motor controls interconnected to the communications network and transmits the same to the micro-controller.
The command module may also include a visual display structure operatively connected to the micro-controller. The micro-controller activates the visual display structure in response to receipt of a predetermined packet of data. The visual display structure may include a plurality of LEDs. Each LED corresponds to a predetermined error condition on the motor wherein the micro-controller activates the corresponding LED in response to a predetermined packet of data received.
The micro-controller may include a plurality of micro-controller executable instructions stored thereon. These instructions allow micro-controller to perform the steps of determining the command signal to be generated in response to a receipt of an activation signal by the micro-controller; generating a command signal; and transmitting the command signal over the communications network. The micro-controller may perform the additional steps of generating a discovery signal for broadcast on the communications network by the communications link and determining the motor control connected to the communications network in response to receipt of a predetermined packet of data. The micro-controller executable instructions may also include the additional step of activating one or more LEDs in response to the receipt of a predetermined packet of data.
In accordance with a further aspect of the present invention, a command module is provided for allowing a user to send commands to one or more motor controls wherein each motor control is operatively connected to a communications network. The command module includes a micro-controller operatively connected to the communications network. The micro-controller generates a command signal for transmission to a predetermined motor control over the communications network. A plurality of user selectable inputs are operatively connected to the micro-controller. Each input provides an activation signal to the micro-controller in response to the user""s selection such that the micro-controller generates the command signal in response thereto. A plurality of configuration devices is also interconnected to the micro-controller. Each configuration device has a plurality of discreet settings such that the command signal generated in a response to the activation signal is determined by the settings of the configuration devices.
It is contemplated that each user selectable input is a pushbutton. Each pushbutton is movable by user between a first non-depressed position and a second depressed position wherein the pushbutton transmits an activation signal to the micro-controller. It is contemplated that a communications link interconnect the micro-controller to the communications network in order that the micro-controller may transmit command signals to the predetermined motor control over the communications network. The communications network may also receive packets of data from the motor controls on the network and transmit the same to the micro-controller.
A visual display structure may be operatively connected to the micro-controller. The micro-controller activates the visual display structure in response to receipt of a predetermined packet of data. The visual display structure includes a plurality of LEDs. Each LED corresponds to a predetermined error condition on the motor wherein the motor control activates a corresponding LED in response to the predetermined packet of data received.
In accordance with a still further aspect of the present invention, a method is provided for providing user selectable commands to a motor control interconnected to a communication network and for displaying the status of various operating parameters of a motor controlled by the motor control. The method comprises the steps of configuring a plurality of an input devices such that each input device corresponds to a predetermined command for the motor control. An input device is selected corresponding to the command desired by the user. A command signal is generated in response to actuation of the selected input device and the command signal is transmitted over the communication network to a motor control.
The method may include the further steps of configuring a plurality of display devices such that each display device corresponds to a predetermined status of an operating parameter of the motor. Packets of data received from the motor control correspond to the status of an operating parameter of the motor. A predetermined display device is illuminated in response to the packet of data received.
The plurality of input devices are configured by providing a plurality of configuration devices. Each configuration device has a plurality of discreet settings. A user sets the configuration devices to a user desired setting such that the user desired settings are provided as a selected combination. Each input device is assigned a corresponding predetermined command for the motor control in response to the selected combination.
The method may also include the additional steps of generating a discovery signal for broadcast on the communications network. In response thereto, each motor control on the network provides a response from which the type of motor control may be determined.